Controlled Microencapsulation of Rejuvenators by Jet Vibration to Promote Self-healing in Bituminous Materials

This study aimed to synthesise enhanced biocapsules containing oil as an additive to promote self-healing in bituminous materials. The capsules consisted of a biopolymeric matrix of sodium alginate as encapsulating material and sunflower cooking oil as a non-hazardous rejuvenating agent. Oil was incorporated in five concentrations by weight of alginate, 1:1, 1:3, 1:5, 1:7, and 1:9, respectively. Thus, five oil-in-water (O/W) emulsions were prepared to synthesise biopolymeric capsules via ionic gelation using an encapsulator device that works by jet vibration technique. The physical properties, stability and droplet size distribution were measured in the O/W emulsions using microscopy techniques and laboratory tests. The morphological and the physical-mechanical properties of the biocapsules were also evaluated. The main results showed that the O/W emulsions increased their viscosity and physical stability when increased the oil content, reducing their creaming rate over time. The synthesised biocapsules presented spherical morphology and high encapsulation efficiency. The size of the produced biocapsules was mainly dependent on the selected nozzle size, the flow rate and viscosity of the extruded O/W emulsions, and the vibrational frequency applied and controlled on the encapsulator device. A reduction in the encapsulated rejuvenator content was quantified in the biocapsules, resulting in a lower volume and higher density and compressive strength values. Finally, the capsules effectively resisted the load associated to on-site compaction in a way that they can be potentially used as an effective additive for asphalt self-healing purposes.